Electrical-wave transmission.



No. 789,124. PATENTED MAY 2, 1905.

C. D. BHRET.

ELECTRICAL WAVE TRANSMISSION.

APPLICATION FILED JUNE 12- 1902.

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'No. 789,124. v M PATENTED MAY 2, 1905. G. D. EHRET.

ELBQTRIGAL WAVE TRANSMISSION.

APPLICATION FILED JUNE 12. 1902.

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PATENT ()FFICE.

CORNELIUS D. EHRET, OF ROSEMONT, PENNSYLVANIA.

ELECTRICAL-WAVE TRANSMISSION.

SPECIFICATION forming part of Letters Patent No. 789,124, dated May 2, 1905.

Original application filed December 3, 1901, Serial No. 84,512. Divided and this application filed June 12,1902. Serial No. 111,241.

To all whom it may concern:

Be it known that I, CORNELIUS D. EHRET, a citizen of the United States. residing at Rosemont, in the county of Montgomery and State of Pennsylvania, have invented new and useful Improvements in Electrical-Wave Transmission, of which the following is a specification.

My invention comprises apparatus for transmitting and amplifying electric waves in signaling, particularly telephony. Its essential feature consists in adding energy to the siggraphic message intended therefor, together with means for amplifying each of the messages so simultaneously transmitted during its transit.

It comprises, further, apparatus for impressing upon a circuit electric waves, preventing their distortion and attenuation by static means, and, further, in reinforcing and amplifying such messages during transit.

So far as I am aware there exists at present no commercially successful telephone relay or repeater. Instruments constructed on the principle of receiving the weakened telephone message in a magnetic receiver and causing such receiver to actuate a microphonic contact in a new circuit are unsuccessful. The distance over which telephone messages are capable of transmission with instruments now in use is limited to one thousand or fifteen hundred miles. This is due to the detrimental effects of distributed capacity, resistance, and leakage of the circuit, which operate to attenuate and distort the current-waves representing the message.

By the system herein disclosed it is pro.- posed to extend the distance over which commercial telephony can be practiced by impressing upon the circuit a high-frequency alternating current, modifying the amplitudes of the wave of such current by and in accordance with sound-waves, and amplifying the alternating-current waves at such points in the circuit where they will have become seriously attenuated. This amplification or boosting effect is accomplished by a piece of apparatus well known in alternating-currentpower work as the induction or i asynchronous generator. In construction the induction-generator is precisely the same as the induction or asynchronous motor. The inductionmotor when driven above synchronous speed becomes a generator and adds energy to the circuit to which it is connected, provided there at all times exist upon such circuit an alternating current to always supply the primary winding with current.

The frequency of the added energy is precisely that of the energy flowing through the primary winding and establishing its initial field.

In my system the, alternating current, which has been modified as to the amplitudes of the currentwaves by the signal transmitting means, is led through the primary winding of the induction-generator, and so acts as a frequency-setter for the generator, and the mechanical energy supplied to the rotating member of the generator appears in the primary winding as boosted or added energy.

In consequence the signal-waves instead of dying out and becoming valueless are reinforced, to the end that communication can be carried on over longer distances than heretofore possible.

Reference will now be had to the drawings for a more detailed description of the system.

Figures 1 and 2 are diagrammatic representations of impressed and modified alternating-current waves. Fig. 3 is a diagram showing a simple circuit in which are inserted at intervals induction-generators. Fig. 4 is a modification of the system, showing metallic circuit and terminal local circuits along with the induction-generators.

Figs. 5 and 6 are diagrammatic views of means for generating the alternating-current waves which are to be impressed upon the circuit. Fig. 7 is a diagrammatic view of one means of modifying the impressed waves in accordance with speech. Fig. 8 is a diagrammatic view of the magnetic-wave form and the resulting secondarywave form obtained in the generating apparatus shown in Fig. 6. Fig. 9 is a graphic representation of the attenuation of the message in transit and the result of boosting at. certainlntervals. Fig. 10 shows another modification of means for modifying the impressed alternating-current waves by and in accordance with sound-waves. Fig. 11 shows ametallic circuit upon which is impressed at the middle points of the circuit the alternatingcurrent waves, which may be termed a central energy system, and which also shows the induction-generators, one in each side of the circuit at each reinforcing-station. Fig. 12 shows a metallic circuit with a modified means of impressing the alternating energy upon it at the middle thereof, along with modified means for varying the alternating energy in accordance with speech. Fig. 13 is a metallic circuit for conveying at the same time two telephonic messages and reinforcing them en route. Fig. 14: shows the generating-station at the middle of a metallic circuit for impressing alternating current upon the same, along with inductance-coils distributed at certain intervals and also the reinforcing induction-generators.

In Fig. 1 is represented a series of high-frequency alternating-current waves. By high frequency is meant such frequency as is high in comparision with the more essential frequencies in sound-waves occurring in human speech. For example, such frequency may be in the neighborhood of fifteen hundred per second or of course much higher. If a current of such frequency be passing over a circuit and if the amplitude of the waves be modified by means of telephonic transmitting devices, the succeeding waves -will be of different amplitudes, as shown in Fig. 2, and a curve tangent to the tops of the waves will graphically represent the sound waves uttered against the telephone transmitter. However, all frequencies of the voice in excess of the frequency of the impressed current will not modify the impressed-current waves, but will exist upon the circuit independently and will practically go to waste. If is is desired to improve the timbre of the received message,the frequency of the impressed waves should be increased above fifteen hundred to whatever limit desirable, for the reason that it is the higher frequencies in the speech which go to make up its quality. However, the higher frequencies can be neglected and articulatespeech obtained by preserving the lower harmonics only.

ternating current of high frequency, one terminal of which connects to earth a and the other to the telephonic transmitter T. The current impressed upon the line is modified by and in accordance with sound-waves by said transmitter T and passes over the circuit to the receiver R and to earth 6. The receiver R is of a type well-known in high-frequency workingsuch, for example, as the two-coil receiver, in which a stationary coil and a coil carrying or operating adiaphragm are connected in series or parallel with each other. At two points in the circuit are shown the induction-generators I, whose primary windings f are in" the line and whose rotors or secondaries are-shown at a" and comprise, as is well-known, a series of short-circuited conductors, there being no electrical connection from said rotor to any external circuit. Suppose the generator A to be at a transmittingstation and the current-Waves to have been modified in accordance with speech by talking into the transmitterT. Aseries of waves exists upon the line as represented in Fig. 2. However, these waves become distorted and attenuated, due to the evil effects of distributed capacity, resistance, and leakage existingin the circuit. At a considerable distance to the right of the transmitting-station, where said waves have become seriously reduced in their energy, they are reinforced by the inductiongenerator I by the relative motion of rotor and stator at aspeed in excess of synchronous speed for the frequency of the impressed-current waves. The waves then pass on and when again attenuated are again reinforced by the second induction-generator I and are eventually received at R with sufficient amplitude to strongly reproduce sound-waves or speech.

Reference is to be had to Fig. 9, in which the ordinates represent amplitudes L of the waves and the abscissae platted along the axis 0 a distances from the transmitting-station. The attenuation follows a logarithmic law and is graphically represented by the curve y n, and in this figure is shown to reach the receiving-station with an amplitude 2 a, provided there has been no boosting. However, by the use of two induction-generators, as is shown in Fig. 3, the current is boosted at onethird and two-thirds distance from the transmitter, so that when received the amplitude instead of being a n is am. It is to be understood, however, that more induction-generators can be inserted in the line, and, furthermore, that at each one a greater amplification may be brought about than is indicated in Fig. 9.

Fig. 4 shows a metallic circuit with a source of alternating-currents of high frequency at v A, which are fed to the primary of the transformer b, in which is located a telephonic transmitter T. The modified waves at high In Fig. 3, A is a dynamic generator of al- 1 pressure pass from the secondary to line and IOC IIC

en route are amplified by the induction-generators I, as in the case shown in Fig. 8. There .are at each relay-station two induction-generators I, as shown, and which may be mount- .ed on the same shaft and driven by the same be used, as shown in Fig. 5, a direct-current generator Gr, supplying current through W,

,aW'ehnelt interrupter, with the resistance a.

Tapped off from the resistance (6 is the primary circuit of the transformer b, which ineludes the telephonic transmitter T.

material.

In Fig. 6, G is a direct-current generator supplying current to the ring 0 of resistance The brush 6 is connected at opposite ends of a diameter, and brush 1' is connected to opposite ends of a second diameter at right angles to the one first named. Brush is also connected to one terminal of the primary of the transformer b. The other terminal of the primary is connected to the telephone-transmitter T and thence to the trailer d, which is driven by belt it, running over pulley 9. As the trailer revolves at high speed, the primary 5 receives a uniformly rising and falling difference of potential at its terminals, and the current resulting therefrom produces a magnetic effect in the core of the transformer, graphically represented in the upper portion of Fig. 8. As a result the secondary waves will be flat-topped, as shown in the lower portion, though in practice they are rounded at their tops. It is desirable, so far as possible, to have broad-topped waves, to the end that the members in the receiver are more uniformly under stress.

In Fig. 7, A represents a generator of alternating currents of a single frequency higher than the more essential frequencies of speech. I) is a transformer in whose secondary circuit are included the battery Band the telephonetransmitter T. By speaking into the transmitter T the amplitudes of the current-waves impressed upon the line-circuit are varied in accordance with speech, as represented in Fig. 2.

In Fig. 10 is shown a core 0, upon which at the upper end is a coil fed from the-generator A, furnishing alternating currents of high frequency-that is, of frequency higher than the more essential voice frequencies. The middle coil is connected to line, and the circuit of the lower coil embraces the battery B and telephonic transmitter T. The latter when spoken into causes, in view of the relation of the windings, a variation in the inductance of the remaining coils, such variation corresponding to speech-waves, the result being an impression upon the line of high frequency alternating current waves whose amplitudes are varied by and in accordance with sound or speech waves.

Fig. 11 shows a metallic circuit with two generators A at the middle point. It represents, in effect, a central-energy system and permits talking from either end of the circuit with equal facility. The ,two generators A must supply currents to the line in synchronism and to that end, if the generators A be similar, should'have their rotating members mounted upon the same shaft. Speaking into the telephonic transmitter T at either end of the circuit varies the amplitudes of the alternating-current waves passing over the same. These as they become attenuated are amplified by the induction-generators 1, of which there are two at each station and preferably have their rotating members mounted upon the same shaft, as stated in connection with Fig. I. I

Fig. 12 shows a metallic circuit with the energy supplied at the middle point from the generator A through the two transformers b b. Synchronism is by this means obtained with certainty, and care should be taken in connecting the transformers to the circuit that they aid each other. As in Fig. 11, two induction-generators are shown at each relaystation, and the terminal stations comprise the 9 5 receivers R, the transformers t, and the telephonic transmitters'T.

In Fig. 13 there are shown the left-hand end and the central-energy stations of a circuit adapted for multiple telephony. Upon the line through the transformersb are impressed alternating currents of different frequenciesone by generator A and the other by generator A. In circuit with the generator A is the condenser C and inductance L. The product of the capacity of C and inductance of L is such as to make the primary circuit, including A, resonant to the frequency generated by A. In connection with the generator A is the condenser C and the ind uctance L, the purpose of Oand L being the same as stated in connection with C and L in the circuit of A. At the relaying-station at each side of the line are shown two induction generators I and 1. In series with I is the inductance L and capacity C, comprising altogether a resonant circuit, which will select out the al ternating current impressed upon the line by the generator A and reinforce it. In circuit with I is the condenser C and inductance L, which, with 1, form a resonant circuit adapted to select out the alternating current supplied by generator A. The rotors of the two induction-generators I are joined on the same shaft, while the rotors of the two induction-generators 1 are upon another shaft, or, in fact, all may be upon the-same shaft and driven by the same prime mover, provided the correct number of poles is supplied. It is seen, therefore, that each current 'ance with sound or speech waves.

is selected out to its proper reinforcing-generator and passes on to the receiving-stations.

The terminal stations shown comprise at one instrument the condenser C inductance L which, together with the primary of the transformer 6, form a resonant circuit adapted to v select out the current impressed upon the line by the generator .A. In the secondary of the transformer b is the condenser-transmitter T, which when spoken into modifies the amplitudes of the alternating-current waves passing through the primary by and in accord- In shunt to the inductance L is the receiver R. It is to be noted that inasmuch as L 0 form a resonant circuit the potential at the terminals R is greater than that across the circuit at the receiving-station. In the other telephone instrument there is shown condenser C in series with inductance L primary of the transformer I), and thereceiver B In the secondary of transformer I) is a simple microphone T. The electrical constants of this telephone set is such as to make it resonant to the current impressed upon the circuit by the generator A, and in consequence a message intended for such receiver will be properly selected out from any other telephonic messages which may be existing upon the circuit at the same time.

In Fig. 14: is shown a middle portion of a metallic circuit in which A is a generator of alternating current of low frequency, supplying current through the transformer b to the circuit C b b L. The constants of the last-named circuit are such that when vibrating freely it has a periodicity of fifteen hundred per second or more. This circuit is charged from the transformer b in conjunction with the alternator A and when fully charged discharges across the spark-gap s and vibrates freely at the above-mentioned rate. There are impressed, therefore, upon the line the required high-frequency alternating waves. However, the means for impressing a high-frequency current on the lines circuit shown in Fig. 12 and other figures may be substituted. At uniform distances along the main circuit are inductance-coils p, which aid in reducing distortion and attenuation of the transmitted waves of single frequency. Induction-generators I are shown as replacing certain inductance-coils of the series, and at these points required in connection with this system. The presence of great masses of iron in the magnetic circuits is objectionable in that the hysteresis effects cause odd harmonics of the impressed alternating-current waves and interfere to some extent with the operation of the system. The generators used in the systems described herein should therefore be specially designed with little or no iron in the magnetic circuits, and the rotors should be of a construction preferably disk-shaped to permit of high rotary velocities.

It has been proposed to use in the ordinary telephone systemthat is, where the current on the line is an extremely complex one having all the different frequencies found in speechan induction-generator for the purpose of reinforcing the complex current during transmission. Such system is unsuccessful, because the different frequencies of the complex current would be reinforced to different extents, thus amplifying greatly the low frequencies and the high frequencies to a far less extent, with theresult that the reproduction of speech would be impossible. In contradistinction to this disadvantage the system herein described'reinforces all voice frequencies equally up to and including the frequency of the current normally existing or impressed upon the line. The result is that the timbre by this system remains or conforms more nearly to the natural than in the proposed system, where the reinforcement is not uniform.

In the transmission of currents over circuits whose length is so great that the wave phenomena are developed occurs distortion and attenuation. In order that each of these evils be a minimum, the ohmic resistance of the circuit should be as small as possible, while the distributed inductance should be as large as possible. For minimum distortion the leakage should be relatively large and the capacity per unit length should be as small as possible. As to the attenuation it is a minimum when the leakage is least and the capacity greatest--that is, the best conditions for distortion and attenuation are opposed when considering the leakage and capacity per unit length. If, however, the attenuation be disregarded and the distortion principally considered, the leakage of the circuit can be made relatively large, and the capacity should be small. To bring about such result, the herein-described system of boosting is advantageous, inasmuch as considerable leakage is permitted due to the possibility of adding energy in as great amounts as necessary, since the transmitted current is of single frequency, and therefore capable of being reinforced by an induction -generator and at such points as desirable. At the same time that such leakage is introduced the danger of too great attenuation is overcome by the presence of the above-mentioned boosters.

To carry this principle into operation, I provide, as shown in Fig. 11 or Fig. 14, leak-circuits 71:, which are distributed over the entire circuit at preferably regular intervals, such intervals being some small fraction of the wave length of the transmitted current. In Fig. 11 such leaks are applied to a circuit in which no inductance-coils are present, whereas in Fig. 14 such leaks l: are provided at the intervals between the inductance-coils p described in connection with such figure above. It is to be understood also that leak-circuits can be applied to all of the arrangements of circuits herein shown. While the leaks may be applied at regular intervals at the rate of a plurality within a wave length, it is to be understood that they may be applied at irregular intervals greater or less than wave length. The leak-circuits is, extending from the circuitwires to earth or joining the two conductors of a circuit, may include high resistances, inductances, or condensers or suitable combinations of the same. However, either resistance or inductance leaks are preferred.

By the herein-described system, inwhich a current of practically constant frequency is impressed upon the line, distortion is reduced by the employment of leakage and may be further reduced by the employment of inductance. The attenuation resulting from leakage and other causes is compensated for or more than compensated for by the inductiongenerator, which reinforces the simple current of practically constant frequency, the waves of different amplitudes being reinforced proportionately to their amplitudes, thus preserving the form of the transmitted energy as originally modified and impressed upon the line. Inductance is not essential to the herein-described system, since distortion can be reduced by leakage and the attenuation then overcome by reinforcement. The greater the amount of leakage the less inductance necessary for keeping the distortion within practical limits. However, it is of advantage to employ inductance and when employed may be obtained by lumped inductances connected in series in the circuit at regular intervals or may be obtained by any other suitable means or distribution, as suggested by Heaviside.

It is to be understood that for any of the telephone transmitters or transmitting devices herein shown and described may be substituted any of the well-known telegraphic transmitters or transmitting devices. Thus a simple telegraphic key, perforated tape-transmitter, or, in fact, any of the transmitters in the art of telegraphy may be employed to control the alternating, fluctuating, or other current impressed upon the circuit. Similarly,-

the telephone-receivers herein shown may be replaced by any suitable telegraph-receivers. In telegraphy the frequency of the fluctuating or alternating current need be a moderate one only'as, for example, ordinary commercial frequencies of from twenty-five to one hundred and thirty-three cycles per second or higher, if desired.

I do not wish to be limited to the precise arrangement of circuits, or means, for generating the alternating currents or for modifying them, for any equivalent devices of those shown may be used and are comprehended in the scope of the appended claims. In fact, either generators of broad-top waves or the more usual generators of sine waves, as A, may be employed.

This application is a division of my application, Serial No. 84,512, filed December 3, 1901.

What I claim as new, and desire to secure by Letters Patent, is

1. In a signaling system, means for impressing upon a circuit an alternating or fluctuating current, means for modifying said current in accordance with a signal to be sent, and an asynchronous or induction generator having a winding associated with said circuit.

2. In a signaling system, means for impressing an alternating, or fluctuating current upon a circuit, means for modifying said current in accordance with a signal to be sent, and an asynchronous or induction generator for reinforcing the transmitted current.

3. In a signaling system, means for impressing electrical energy upon a circuit, means for modifying said energy in accordance with a signal to be sent, means for causing leakage of said energy at intervals along the circuit, means for reinforcing the transmitted energy, and means for reproducing the signal.

4:. In a telephone system, a source of alternating or fluctuating current of a frequency higher than the frequencies of the more essential frequencies found in speech, a transmitter for modifying said current by and in accordance with speech, a circuit upon which said modified current is impressed, an asynchronous or induction generator associated with said circuit for reinforcing the transmitted current, and a receiver for reproducing speech.

5. In a telephone system, means for impressing upon a circuit an alternating or fluctuating current, a transmitter for modifying said current by and in accordance with speech, means permitting leakage of said current, means for reinforcing said current, and a receiver for reproducing speech.

6. In combination, a circuit, means for impressing upon said circuit an alternating or fluctuating current of practically constant frequency higher than the frequencies of the more essential components of the voice, means for modifying said current by and in accordance with speech, lumped inductances inserted in said circuit at practically uniform intervals, said intervals being a fraction of the length of the transmitted waves of said alternating current, leaks associated with said current, means for reinforcing the transmitted current,

and a receiver in said circuit for reproducing speech.

7. In combination, a circuit, means for impressing upon said circuit an alternating or fluctuating current of practically constant frequency higher than the frequencies of the more essential components of the voice, means for modifying said current by and in accordance with speech, an induction-generator in said circuit driven at a speed in excess of the synchronous speed corresponding with the frequency of the impressed alternating current, and a receiver in said circuit for reproducing speech.

8. In combination, a circuit, means for impressing upon said circuit an alternating or fluctuating current of practically constant frequency higher than the frequencies of the more essential components of the voice, means for modifying said current by and in accordance with speech, lumped inductances inserted in said circuit at practically uniform intervals,

said intervals being a fraction of the length of the transmitted waves of said alternating current, leaks associated with said circuit, an induction-generator associated with said circuit for reinforcing the transmitted current, and a receiver in said circuit for reproducing speech.

9. In combination, a circuit, means for impressing upon said circuit an alternating or fluctuating currentof-a frequency higher than the frequencies of the more essential components of the voice, means for modifying said current by and in accordance with speech, lumped leaks applied to said circuit at practically uniform intervals, a booster for reinforcing the transmitted current, and a receiver in said circuit for reproducing speech.

10. In combination, a circuit, means for impressing upon said circuit an alternating or fluctuating currentof a frequency higher than the frequencies of the more essential compo nents of the voice, means for modifying said current by and in accordance with speech, lumped inductances and leaks applied to said circuit at practically uniform intervals, said intervals being a fraction of the length of the transmitted waves of said alternating current, means for reinforcing the transmitted current, and a receiver in said circuit for reproducing speech.

11. In combination, a circuit, means for impressing upon said circuit an alternating or fluctuating current of a frequency higher than the frequencies of the more essential components of the voice, means for modifying said current by and in accordance with speech, lumped inductances and leaks applied to said circuit at practically uniform intervals, said intervals being a fraction of the length of the transmitted waves of said alternating current, an inductiongenerator associated with said circuit for reinforcing the transmitted current, and a receiver in said circuit for reproducing speech.

12. In combination, acircuit rendered practically distortionless by lumped inductances and leaks distributed at practically uniform intervals, and means for reinforcing the transmitted current as attenuated by said leaks.

13. In a signaling system, a circuit rendered practically distortionless for a current of predetermined frequency by means of lumped inductances and leaks applied to said circuit at practically uniform intervals, and an induction-generator connected in said circuit and operating at a speed in excess of the synchronous speed corresponding with the frequency of said current, said induction-generator operating as a booster to compensate for the attenuation caused by said leaks.

14. In a signaling system, a practicallydistortionless circuit having a source of leakage associated therewith, and means associated with said circuit to reinforce the transmitted current to compensate for the leakage cooperating to render said circuit distortionless.

15. In a signaling system, a circuit rendered practically distortionless by inductance and leakage distributed at practically uniform intervals along said circuit, means located intermediate the transmitting and receiving stations for impressing electric energy upon said circuit, and means for reinforcing the transmitted energy to compensate for the attenuation caused by said leaks.

16. In combination, acircuit rendered practically distortionless by inductance and leakage, and an induction-generator for reinforcing the transmitted current to reduce the attenuation thereof.

17. In combination, a circuit, means forimpressing upon said circuit an alternating or fluctuating current of a frequency higher than the more essential voice frequencies, means for modifying said current by and in accordance with speech, inductances and leaks applied to said circuit, means associated with said circuit for reinforcing the attenuated current, and a receiver to reproduce speech.

1.8. In combination, a circuit, means for impressing upon said circuit intermediate the transmitting and receiving stations an alternating or fluctuating current, means for modifying said current in accordance with the message to be transmitted, an induction-generator for reinforcing said current as modified, and a receiver to reproduce the message.

19. In combination, a circuit, means forimpressing upon said circuit intermediate the transmitting and receiving stations an alternating or fluctuating current, means for modifying said current in accordance with the message to be sent, leaks applied to said circuit, means for reinforcing the transmitted current, and a receiver to reproduce the message.

20. In combination, a circuit, means for impressing upon said circuit an alternating or fluctuating current of practically constant frequency, means for varying the amplitudes of the waves in accordance with the message to be sent, an induction-generator for reinforcing said current, and a receiver to reproduce the message.

21. In combination, acircuit rendered practically distortionless by inductance and leakage, and means for reinforcing the transmitted current.

22. In combination, a circuit, means for impressing uponsaid circuit an alternating or fluctuatingcurrent of practically constant frequency, inductance cooperating with leaks distributed along said circuit to reduce the distortion of the waves of said current, means for modifying said current in accordance with the message to be sent, means for reducing attenuation of said current, and a receiver to reproduce the message.

23. In combination, a circuit. leaks associated therewith, means for impressing upon said circuit a current fluctuating at practically constant frequency, means for modifying said current in accordance with a message to be sent, means for reinforcing said current, and a receiver for reproducing the message.

24. In combination, a circuit, leaks associated therewith, means for impressing upon said circuit a current fluctuating at practically constant frequency, means for modifying said current in accordance with a message to be sent, inductances associated with said circuit, a plurality within a wave length for reducing distortion of the current-Waves, and a receiver for reproducing the message.

25. In combination, a circuit, means for impressing upon said circuit a current fluctuating at practically constant frequency, means for modifying said current in accordance with a message to be sent, ind uctances and leaks associated with said circuit for reducing the distortion of the current-waves, means for reinforcing the transmitted current and a receiver for reproducing the message.

26. In combination, a circuit, means for impressing upon said circuit a current fluctuating at practically constant frequency, means for modifying said current in accordance with the message to be sent, leaks for reducing the distortion of the current-waves, means for reinforcing the transmitted current, and a receiver for reproducing the message.

27. In combination, acircuit rendered practically distortionless by inductance and leakage, and a booster associated with said circuit.

28. In multiple telephony, a circuit, means for impressing upon said circuit a plurality of fluctuating currents of diflerent frequencies, means for modifying each of said currents by and in accordance with speech, means for selecting each modified current to a branch attuned to its frequency,abooster in each branch, and a receiver for each transmitted current.

29. In multiple telephony, acircuit, means for impressing upon said circuita plurality of fluctuating currents of different frequencies, means for modifying each of said currents by and in accordance with speech, leaks for reducing distortion of each transmitted current, means for reinforcing each of said modified currents, and means for selecting each modifled current to a circuit attuned to its frequency.

30. In a multiplex-signaling system, a circuit, means for impressing upon said circuit a plurality of fluctuating currents of different frequencies, means for modifying each current in accordance with a message to be sent, leaks for reducing distortion, means for reinforcing a modified current independently of the other currents, and means for selecting each modified current to a predetermined receiver.

31. In a multiplex-signaling system, a circuit, means for impressing upon said circuit a plurality of fluctuating currents of different frequencies, means for modifying each of said currents in accordance with a message to be sent, an induction-generator for reinforcing each of said modified currents, and means for selecting each modified current to a predetermined receiver.

32. In a multiplex-signaling system, a circuit, a plurality ofmeans for impressing upon said circuit a plurality of fluctuating currents of different frequencies, means for modifying each of said currents in accordance with the message to be sent, selecting each of said modified currents to a circuit selective of it, means in each selective circuit for reinforcing the modified current traversing the same, and means for selecting each modified current to a predetermined receiver.

33. The combination with a signaling-circuit, of means for causing leakage, and means for reinforcing the transmitted current.

34. The combination with a signaling-circuit, of leaks applied thereto for reducing distortion, and means for reinforcing the transmitted current to reduce attenuation.

35. The combination with a signaling-circuit, sources of inductance and leakage for reducing distortion, and means for reinforcing the transmitted current for reducing attenuation 36. The combination with a telephone-circuit, of means for causing leakage, and means for reinforcing the transmitted current.

37. The combination with a telephone-circuit, of means for causing leakage to reduce distortion of the transmitted current-waves, and means for reinforcing the transmitted current for reducing attenuation.

38. The combination with a signaling system, of means for causing leakage, and an asynchronous or induction generator for reinforcing the transmitted current.

39. The combination with a telephone-circuit, of means for causing leakage to reduce distortion, and an asynchronous or induction generator for reducing attenuation of the transmitted current.

40. In a signaling system, a circuit, means for impressing upon said circuit a fluctuating or alternating current, means for modifying said current in accordance with a signal to be sent, and an asynchronous or induction generator for reinforcing the transmitted current.

41. In a telephone system, a circuit, means for impressingupon said circuit an alternating or fluctuating current, means for modifying said circuit by and in accordance With speech, and an asynchronous or induction generator for reinforcing the transmitted current.

CORNELIUS D. EHRET.

Witnesses:

ALICE T. BURROUGH, MAE HOFMANN. 

